1. Field of the Invention
The present invention is directed to a rechargeable electrochemical battery, and more particularly to a biocompatible, rechargeable electrochemical battery configured as a wire for powering a device to be implanted in, or proximate to a living organism, as well as any other device requiring non-traditional battery forms.
2. Discussion of the Related Art
Recently, the number of implantable medical devices has dramatically increased. For example, over the last decade, the use of stents, drug eluting stents, pacemakers, defibrillators, ventricular assist devices, glucose infusion pumps and neurostimulators has increased many fold. Some of the above enumerated examples, as well as a number of other implantable and/or non-implantable medical devices are active devices and require power sources for operation. Power sources or batteries that are utilized in conjunction with implantable or non-implantable medical devices typically have stringent specifications imposed on them relative to physical size and performance. Older generation batteries that were designed for implantable medical devices were larger devices with a relatively short useful life. However, with the advent of miniature implantable medical devices for such diverse applications as drug delivery, glucose sensing and monitoring, and neurostimulation, batteries capable of providing useful power and occupying ever smaller volumes are required. In addition to small size, a battery that is to be implanted should preferably include a useful life, insignificant self-discharge rates, a high reliability over a long time period, and compatibility with a patient's internal body chemistry, in other words, it should be as biocompatible as possible. Biocompatible coatings and/or encapsulants may be utilized to meet this need.
Certain battery chemistries, for example, lithium chemistries, require that the battery be hermetically sealed; however, hermetic packaging may make non-standard form factors difficult to achieve. Accordingly, different chemistries may be utilized to eliminate the need for a hermetic seal.
The devices briefly described above are considered to include some of the more traditional energized or power consuming implantable devices. More recently, it has been theorized that active components or components that require energy may be incorporated into traditionally passive devices. For example, contact lenses have provided vision correcting functionality through the incorporation of a refractive quality into the lens. In addition, pigmentation changing qualities may be incorporated into contact lenses to provide cosmetic enhancement, and agents and/or drugs may be incorporated into contact lenses to provide therapeutic functionality. These characteristics are accomplished passively or without the contact lens being energized. Another device that operates in a passive mode is a punctal plug which is utilized to treat dry eyes by slowing the removal of tears through the punctum. However, as stated above, it has been theorized that active components may be incorporated into traditionally passive devices such as contact lenses and/or punctual plugs. For example, an active component of a contact lens may be able to change the refractive power of the lens. In addition, a punctual plug may comprise a microscale sized pump for dispersing a therapeutic agent. As used herein, a punctal plug refers to a device of a size and shape suitable for insertion into the inferior or superior lacrimal canaliculus of the eye through, respectively, the inferior or superior lacrimal punctum.
Accordingly, there exists a need for power supplies in batteries that are compatible with the size and shape requirements of these devices as well as the energy requirements of these new active components. These miniature or micro scale batteries should provide a useful power output, be capable of charging at acceptable rates, have a useful cycle life, be capable of operating for extended periods in a deep discharge modality and substantially safeguard against the risk of electrolyte leakage.